If your boat lives in the water, marine growth can build up quickly on the hull. This can slow the boat down, increase fuel use, affect performance, and make the hull harder to clean later.
Antifoul paint helps reduce marine growth below the waterline and keeps your boat performing better between haul outs.
If you are planning to antifoul your boat yourself, the most important part is preparation. The paint you choose matters, but the surface underneath matters just as much.
Step 1: Find Out What Antifoul Is Currently on the Boat
Before buying new antifoul, try to find out what product is already on the hull.
This is important because not all antifoul paints are compatible with each other. If the wrong product is applied over the top, it may not stick properly or it may react with the existing coating.
If you know what antifoul is already on the boat, it is much easier to choose a compatible product and follow the correct preparation steps. We have the steps below if you don't know what antifoul you have on the boat.
Step 2: Choose the Right Antifoul
Once you know what is already on the boat, you can choose the right antifoul for your hull, boat use, and local water conditions.
Different boats need different products. A boat that sits in a marina most of the year may need something different to a boat that is used regularly. The hull material also matters, especially if the boat is fibreglass, aluminium, timber or steel.
At Boat Harbour Marine, we stock quality antifoul products from brands including International, Jotun and Altex No. 5.
We also stock antifoul primer, thinners and application products to help with the full job, not just the paint itself.
If you are unsure which antifoul you need, bring in as much information as possible about your boat, the current coating, hull material and how the boat is used.
Step 3: If You Do Not Know the Existing Antifoul, Use a Primer
If you do not know what antifoul is currently on the boat, the safest approach is usually to use a suitable primer or tie-coat before applying the new antifoul.
A primer helps create a barrier between the old unknown coating and the new antifoul. This can reduce the risk of compatibility issues and help the new antifoul adhere properly.
This is especially important if the old antifoul is patchy, very worn, flaking, or you are changing brands.
Always check the product instructions and technical data sheet for the antifoul and primer you are using. The correct primer, drying time and overcoating window can vary depending on the product.
Step 4: Inspect the Hull for Damage
Before sanding or painting, inspect the hull properly.
Look for:
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Chips or cracks in the fibreglass
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Exposed fibreglass or gelcoat
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Blisters
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Flaking paint
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Soft or damaged areas
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Scrapes from trailers, beaches or moorings
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Damage around the keel, chines, transom or waterline
If there is damage to the fibreglass, it should be repaired before antifouling. Antifoul is not designed to fix structural damage, seal cracks, or repair exposed fibreglass.
Small chips or scratches may need to be sanded, filled, faired and primed before painting. More serious fibreglass damage should be assessed and repaired properly before any antifoul is applied.
Painting over damage can trap moisture, hide problems and lead to bigger repair issues later.
Step 5: Clean the Hull
The hull needs to be clean before you start sanding or painting.
Remove slime, salt, loose growth, dirt and any residue from the surface. A pressure wash is often used after haul out, followed by further cleaning where needed.
The surface should be dry, clean and free from grease, oil, dust and loose paint before you start applying primer or antifoul.
Good preparation is what helps the antifoul last.
Step 6: Sand or Prepare the Existing Antifoul
Once the hull is clean, the existing antifoul usually needs to be sanded or lightly abraded so the new coating has something to grip to.
Any loose, flaky or unstable antifoul should be removed. The surface needs to be sound before you paint over it.
Use the correct sanding paper or sanding discs for the job and always wear the right protective gear. Antifoul dust is not something you want to breathe in, so wet sanding is often preferred to reduce dust.
Do not dry sand antifoul without proper safety equipment and suitable dust control.
Step 7: Mask the Waterline and Fittings
Before painting, mask up the waterline so you get a clean finish.
You should also protect areas that should not be painted, such as:
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Anodes
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Transducers
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Propellers, unless using the correct product
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Shafts and fittings, depending on the coating system
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Trailer rollers or pads if the boat is on a trailer
Using proper marine masking tape helps keep the job cleaner and makes the final result look much better.
Step 8: Prime Where Needed
If the hull has bare patches, exposed fibreglass, repaired areas, or unknown existing antifoul, apply the correct primer before antifouling.
Primer is used to help with adhesion and compatibility. It can also help seal repaired or exposed areas before the antifoul goes on.
The right primer will depend on the hull material and antifoul product being used.
This is where it is important to follow the manufacturer instructions carefully. Primer and antifoul products have specific drying times and recoat windows, and these should not be guessed.
Step 9: Apply the Antifoul
Once the hull is clean, repaired, sanded, masked and primed where needed, you can apply the antifoul.
Stir the antifoul thoroughly before use, as the active ingredients can settle in the tin.
Most antifoul is applied with a roller, with a brush used for edges, corners and around fittings. Apply the recommended number of coats and pay extra attention to high-wear areas such as the leading edge of the keel, rudder, waterline and around the bow.
Always follow the product instructions for:
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Number of coats
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Drying time
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Recoat time
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Launch time
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Thinner requirements
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Suitable roller or brush type
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Hull compatibility
Do not thin antifoul unless the product instructions say to. If thinner is required, use the correct thinner for that brand and product.
Step 10: Launch Within the Recommended Time
Antifoul products usually have a recommended launch window. This means the boat may need to go back in the water within a certain timeframe after painting.
If it is launched too soon or left too long before launching, the performance of the antifoul may be affected.
Always check the tin or product data sheet before applying so you know the timing before you start.
DIY Antifoul Products Available in Brisbane
Boat Harbour Marine stocks a range of DIY antifoul products and marine painting supplies in Brisbane, Redcliffe, Scarborough, Newport, Moreton Bay and the surrounding Queensland area.
We stock antifoul from trusted marine brands including International, Jotun and Altex No. 5.
We also stock antifoul primer, marine thinners, rollers, brushes, sanding discs, sandpaper and other products needed to prepare and apply antifoul properly.
If you are looking for antifoul paint in Brisbane, boat antifoul near Redcliffe, DIY antifoul supplies in Moreton Bay, or marine paint at Scarborough Marina, visit Boat Harbour Marine.
We can also order in other specific antifoul brands or marine paint products if you are trying to match what is already on your boat.
If you are unsure what antifoul is currently on your hull, what primer you need, or which product is suitable for your boat, come in and speak with us.
